June 2004 - Boost - lists.preview.boost.org

CVS temporarily disabled
by David Abrahams 09 Jun '04

09 Jun '04

http://sourceforge.net/docman/display_doc.php?docid=2352&group_id=1#1086711… ( 2004-06-08 09:17:17 - Project CVS Service ) As of 2004-06-08 at 09:16 Pacific, developer CVS services have been disabled for some unplanned maintenance. We do not currently have an ETA for the duration of this outage but we do hope to minimize it as much as possible. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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RE: [boost] Re: Thread lib (good reason for static)
by Hurd, Matthew 09 Jun '04

09 Jun '04

> Behalf Of Eric Niebler > Sent: Wednesday, 9 June 2004 9:15 AM > To: boost(a)lists.boost.org > Subject: [boost] Re: Thread lib (good reason for static) > > Hurd, Matthew wrote: > >>Behalf Of scott > >>Assume use of a technique like the following (think this has been > >>presented as "object shim"?); > >> > >>T & > >>anastasia() > >>{ > >> static T *p = new T; > >> return *p; > >>} > >> > >>as a means of dealing with global construction issue, i.e. instead > >>of expressions like "anastasia.data_member" the usage is > >>"anastasia().data_member". Also assume that some of these global > >>objects (i.e. shims) deploy mutexes for MT reasons. What happens > >>when there is more that one thread running around making calls > >>to shims? Instantiation of the global itself becomes an MT issue. > > > > > > That's what the double-checked locking pattern for singletons is for. > > > > Regards, > > > > Matt Hurd. > > > No, the double-checked locking pattern is only good as the subject of > talks describing why it's not good for anything. > > http://www.nwcpp.org/Downloads/2004/DCLP_notes.pdf Thanks. They are good notes. I'm aware of the portability issues. Doesn't mean you can't have valid platform specific singleton implementations that use the double checked locking pattern. The performance of the approach is too important to give up. Locking is slow. There are a lot of things you can't do portability in C++ which is one rationale for having libraries :-) Regards, Matt Hurd. _______________ Matt Hurd +61.2.8226.5029 hurdm(a)sig.com Susquehanna _______________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

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boost::any question
by Trey Jackson 08 Jun '04

08 Jun '04

All, I just started looking at boost::any, pretty nice. I looked at the implementation, and it uses (as you know) a pointer to an object (w/virtual methods) on the heap, and typeid to determine if conversion is possible. I understand the memory implications (a new object copied on heap). But I'd like to get a better handle on performance, namely: I'm unfamiliar with typeid - and how it's implemented. Does anyone have good pointers to how typeid is generally implemented? Or even specifically: I'm using gcc3.x on RH Linux. I'd just like to avoid/guarantee I'm not going to be hit by some O(N) look-up for using typeid a lot. thanks, TJ -- Trey Jackson tjackson(a)ichips.intel.com "Her hair glistened in the rain like nose hair after a sneeze." -- Chuck Smith, Woodbridge

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Problem with mpl::iter_fold_if.hpp in vacpp 6.0
by Joaquín Mª López Muñoz 08 Jun '04

08 Jun '04

Regression tests show the following at different locations: "/home/tk/boost_regression/boost/boost/mpl/iter_fold_if.hpp", line 104.11: 1540-0038 (S) The name "typename result_::state" is not a type. I don't know how easy to fix this can be (for those who know the internals of MPL). Currently, the problem breaks uBLAS and multi_index. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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Problem building bjam executable
by Bart Garst 08 Jun '04

08 Jun '04

I'm trying to build the bjam executable by running build.bat from the boost/tools/build/jam_src directory. Here's what I get: C:\BOOST\TOOLS\BUILD\JAM_SRC>build.bat vc7 ### ### "Unknown toolset: vc7" ### ### You can specify the toolset as the argument, i.e.: ### .\build.bat msvc ### ### Toolsets supported by this script are: borland, como, gcc, gcc-nocygwin, intel-win32, metrowerks, mingw, msvc, vc7 ### I also tried running vcvars32 prior to build.bat and got this: C:\BOOST\TOOLS\BUILD\JAM_SRC>"e:\program files\microsoft visual studio .net\vc7\bin\vcvars32" C:\BOOST\TOOLS\BUILD\JAM_SRC>"E:\Program Files\Microsoft Visual Studio .NET\Common7\Tools\"vsvars32.bat Setting environment for using Microsoft Visual Studio .NET tools. (If you also have Visual C++ 6.0 installed and wish to use its tools from the command line, run vcvars32.bat for Visual C++ 6.0.) C:\BOOST\TOOLS\BUILD\JAM_SRC>build.bat vc7 Setting environment for using Microsoft Visual Studio .NET tools. (If you also have Visual C++ 6.0 installed and wish to use its tools from the command line, run vcvars32.bat for Visual C++ 6.0.) The system is Windows NT 4.0 SP6. I'm using a fresh cvs checkout of the entire boost source tree. I'd appreciate any help I can get with this. Thx, Bart

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[assignment library post review]
by Thorsten Ottosen 08 Jun '04

08 Jun '04

Dear All, The post review version can be downloaded from http://tinyurl.com/38c7d Since the review this has changed: 1. insert()/assign() functions has been renamed to reflect which function that is called. So now push_back() is used for vector etc. 2. One header for each standard container. 3. New functions to allow for direct initialization: vector<int> v = list_of(1)(2)(3)(4)(5); map<string,int> m = map_list_of( "Foo", 1 )( "Bar", 2 ); 4. New heavily improved documentation 5. Support for arbitrary functions s.t. new types can benefit from the syntax easily. 6. removal of all half-backed stuff that nobody wanted 7. arguments are forwarded by value instead of const-reference. Reference is a pain to deal with when it comes to string literals. 8. A real test-suite has been added 9. portability has suffered a bit, but that can be solved later. Any comments about docs/implementation are welcome. There is one major isssue we must resolve: What should we call this library. Here are some choices: 1. Initialization library 2. Assignment library 3. Populate library 4. List library I personally would like Boost.List because the library is all about making list for use in various context. best regards Thorsten

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[prereview request][fsm]
by Andreas Huber 07 Jun '04

07 Jun '04

Dear Boosters I think boost::fsm has finally reached a state that is worthy of a formal review. The .zip can be found here: http://boost-sandbox.sf.net/fsm.zip The docs are also available online: http://boost-sandbox.sf.net/libs/fsm As always: Feedback is highly welcome. Regards, Andreas

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[spirit] rule<> and copying
by Thorsten Ottosen 07 Jun '04

07 Jun '04

Hi, I've been using spirit for some config-file parsing. I have some questions: 1. why can we not copy a rule<> ? 2. if we shouldn't copy a rule, why is copying not disabled? It has been a source of errors in my code that I forgot & on my return value. br Thorsten

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token_iterator comments, suggestions
by Gennadiy Rozental 07 Jun '04

07 Jun '04

Hi, For long time in my daytime projects I was using my class token_iterator designed based on old iterator_adaptor design (adopted for old compilers). Now when need arose for such functionality in Boost.Test. I looked in direction of boost::token_iterator. After some struggle I end up adopting my version to new design. Here some of comments and issues that made me opt so. 1. token_iterator follows in a sense a Policy-based design (PBD). Where TokenizerFunc is a Policy that implements most of the functionality. The problem here IMO (unfortunately you see it now quite frequently), that I do not see a reason to use such a design. PBD makes sense it your generic component do a lot of work, provide common interface, combine several independent policies. In this case most what token_iterator does is just a forwarding (it become especially clear if you switch to use input_iterator_adaptor). It wouldn't be that bad, but PBD in this case causes significant usability inconvenience. Instead of plain and simple: token_iterator it( "a:b", ":" ); I have to write something like: token_iterator<char_delimiters_separator<char> > it( char_delimiters_separator<char>( ":" ), "a:b" ). All of that just because we have separate notion of Tokenizer function. IMO it too big price to pay. My suggestion is to get rid of the TokenizerFunction notion. Just implement many different iterators with the same scope of interest: tokenization. We will need to find proper names for iterators and instead of TokenizerFunc model description we may have page explaining how to write custom token iterators (if necessary, which I doubt). 2. token_iterator deals with begin/end iterators. I understand that in some rare cases there is need to iterate over range of iterators (BTW, std::input_iterator gonna be bad example - did you ever tried to use token_iterator over it?). But in most case we want to tokenize a string. And in most cases it either std::string or [char|wchar_t] const*. The fact that Iterator is a template parameter makes token_iterator usage quite inconvenient. In most cases the only template parameter that is required is IMO character type. My suggestion: lets have 2 different types if token iterators: one to iterate over string and separate to iterate over range of iterators. 3. I found it confusing in many cases how delimiters gets specified in token_iterator: token_iterator( "...", ":", " " ) Which string represent dropped delimiters, which kept? And what if I just want empty tokens? I need to write token_iterator( "...", "", "", keep_empty_tokens ) What are these two empty strings doing here?My suggestion is to use named parameters scheme. Like this: token_iterator( "...", dropped_delimiters = ":", kept_delimiters = " " ); 4. 2 Tokenizer functions use Traits as *policy* parameter. What actually is required in Compare predicate, that may or may not be implemented using char_traits. While std::basic_string references inside tokenizer function implementation should refer to traits by name std::char_traits 5. What if I want to use isspace as kept delimiters policy? There is no way to specify that. IMO delimiter policy should be separated (as runtime policy). 6. You use iterator_category as a selector of assigner. It's better to use traversal instead 7. In many places you use #if !defined(BOOST_MSVC) || BOOST_MSVC > 1300 typename #endif use BOOST_DEDUCED_TYPENAME instead 8. What is the purpose of token_iterator_generator. I do not see a need for one with new iterator facade design. 9. Why would we need all the access methods? Iterator base()const{return begin_;} Iterator end()const{return end_;}; TokenizerFunc tokenizer_function()const{return f_;} Type current_token()const{return tok_;} bool at_end()const{return valid_;} I couldn't imagine why do we need them. 10 Token iterator asserts in attempts to dereference or iterate end iterator. I don't believe it's correct. In many cases (mostly in design that assumes some optional tokens in the end) it's much more convenient this does not happened. My suggestion is to return empty token on dereference and stay quite on iteration. 11. In simpler design there won't be need in template copy constructor for token_iterator 12. Documentation need to be updated IMO, cause even as things stands now it dies not represent the best practice moved from type generators usage. 13. Files under libs/tokenizer lacks any structure required by boost standards. 14. There is no real test suite only some small examples supplied. 15. Why escaped_list_separator was named this way. It seems strange to emphasize in a name the fact that it use escape symbols, while major separations is that it is CSV list iterator - and this is how I would name it I implemented string_token_iterator and range_token_iterator for use in Boost.Test. See here (in a couple hours) http://tinyurl.com/28db9 for implementation and here http://tinyurl.com/287uk for test suite. Regards, Gennadiy.

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Serializer and when to stop
by Darren Cook 07 Jun '04

07 Jun '04

I'm using boost::serializer between two programs: the first creates the data then serializes it, the second loads that data in and analyzes it. When I had just 420 data samples it all worked fine: I create a vector<Sample> in memory, serialized it and loaded it in the other side. When I moved to 7000 data samples the first program, the creator, sucked all the memory from the machine and then some. So I moved to serializing each data sample as it was created. To read it back in I changed my code from this: std::ifstream input_file(fname,std::ios::binary); boost::archive::binary_iarchive archive(input_file); std::vector<Sample> samples; archive>>samples; input_file.close(); Into this: std::ifstream input_file(fname,std::ios::binary); boost::archive::binary_iarchive archive(input_file); std::vector<Sample> samples; samples.reserve(8000); while(!input_file.eof()){ Sample s; archive>>s; samples.push_back(s); } input_file.close(); But every time it fails with an assert [1]. This seems to be when it has reached end of file. I cannot know in advance how many data samples I'll write to disk, so it seems I have three options: A: Make a special "zero" version of Sample to mark end of file B: At end of program 1 write the number of samples to a special file, and read that in before starting the above loop, so I know when to stop. C: Alter the serializer class to throw exception instead of an assert; I can then catch it and carry on. What is the best way? Is adding a terminator byte to boost::serializer an option (i.e. so I don't have to make a terminator version of each data structure I want to serialize). Incidentally my above loop does a copy of each sample as it adds it to the vector. Is the above code going to be common enough to make it worth including into boost::serializer as a helper function, which could then be optimized with in-place construction or something clever like that? (And then it could handle the termination handling itself as well.) Darren [1]: /usr/local/src/boost_1_31_0/boost/archive/basic_binary_iprimitive.hpp:119: void boost::archive::basic_binary_iprimitive<Archive, IStream>::load_binary(void*, unsigned int) [with Archive = boost::archive::binary_iarchive, IStream = std::basic_istream<char, std::char_traits<char> >]: Assertion `count == static_cast<size_t>(is.gcount())' failed.

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